(1) Field of the Invention
The present invention relates to a submarine cable protecting device which is installed at various locations which are susceptible to seashore waves or sea currents.
(2) Description of the Related Art
Transmission of various signals by coaxial cables or optical fiber cables is carried out through submarine cables which are installed at sea bottom and seashore locations. There are types of the submarine cables for shallow locations and for deep water locations. Since terminal stations for transmitting and receiving the signals are based on land, land-based and submarine cable systems which connect the terminal stations and the submarine cables are needed.
Submarine cable protecting devices are provided to protect the submarine cables installed at locations which are susceptible to seashore waves or sea currents. The submarine cable protecting devices are in a generally cylindrical shape and enclose the submarine cables therein. In order to prevent the submarine cables from being influenced by the seashore waves and stones or the sea currents, the submarine cable protecting devices are made of a metallic material and have a certain weight. The total length of the submarine cables installed in such locations is normally in a range between 200 meters and 300 meters, and the maximum length of the submarine cables may exceed 5 kilometers.
It is desirable to provide a submarine cable protecting device which safely protects the submarine cables and allows the installing work of the submarine cables in such locations to be easily performed.
FIGS. 1A and 1B show a half member 1 of a conventional submarine cable protecting device. A plurality of pairs of the half members 1 form the conventional submarine cable protecting device. FIG. 1A and FIG. 1B are a side view and a bottom view of the half member 1.
As shown in FIGS. 1A and 1B, the half member 1 comprises a cylindrical portion 2 which longitudinally extends along a central axis of the half member 1. The cylindrical portion 2 has a semicircular cross section.
In the half member 1, an outside cylindrical surface 3 extending from a rear end of the cylindrical portion 2 is formed. The outside cylindrical surface 3 has an outside diameter greater than an outside diameter of the cylindrical portion 2.
An inside cylindrical surface 4 extending from a front end of the cylindrical portion 2 is formed. The inside cylindrical surface 4 has an inside diameter greater than the outside diameter of the outside cylindrical surface 3. The inside cylindrical surface 4 is shaped such that the inside cylindrical surface 4 of this half member 1 encompasses the outside cylindrical surface 3 of another half member 1 when the two half members 1 are connected in series.
A pair of fitting lugs 5 on the sides of the cylindrical portion 2 at the rear end thereof near the outside cylindrical surface 3 and at the front end thereof near the inside cylindrical surface 4 are formed. The fitting lugs 5 outwardly project from the sides of the cylindrical portion 2. Each of the four fitting lugs 5 at the front and rear ends of the cylindrical portion 2 has a bolt insertion hole 6. The fitting lugs 5 and the bolt insertion holes 6 are used to position the cylindrical portions 2 of a pair of the half members 1 when they are attached to each other.
The half member 1 of FIGS. 1A and 1B is integrally formed through casting of a cast iron or the like. The half member 1 of the conventional submarine cable protecting device is formed from such a material such that it has a sufficient thickness and a sufficient weight. The conventional submarine cable protecting device has a strength sufficient to withstand the influences of seashore waves or sea currents.
FIG. 2 shows the conventional submarine cable protecting device 9 which is assembled with a plurality of pairs of the half members 1 of FIGS. 1A and 1B. After the conventional submarine cable protecting device 9 is assembled, the conventional submarine cable protecting device 9 encloses a submarine cable 8 therein and protects the same from the influences of seashore waves or sea currents at the installation locations.
The conventional submarine cable protecting device 9 is assembled while the submarine cable 8 is enclosed therein as shown in FIG. 2. The pairs of the half members 1 are continuously installed in series in one direction only, for example, in the direction from the left to the right.
The outside cylindrical surface 3 of each half member 1 is placed on the right side of FIG. 2, and the inside cylindrical surface 4 is placed on the left side of FIG. 2. Bolts 11 are inserted into the bolt insertion holes 6 of the half members 1, nuts 12 are attached to the bolts 11, and they are tightened together. In this manner, the pairs of the half members 1 are continuously connected to each other in series.
When a pair of the half members 1 is coupled to each other, the outside cylindrical surfaces 3 of the two members form an outside cylindrical surface 13 at the right end of the two members, and the inside cylindrical surfaces 4 of the two members form an inside cylindrical surface 14 at the left end of the two members. As described above, the inside cylindrical surfaces 4 have an inside diameter that is greater than the outside diameter of the outside cylindrical surfaces 3.
Therefore, when the pairs of the half members 1 are continuously installed in series in the direction from the left to the right, as shown in FIG. 2, the outside cylindrical surface 13 in one pair of the half members 1 which was previously installed is encompassed by the inside cylindrical surface 14 in another pair of the half members 1 which is presently to be installed. There is a small clearance between the outside cylindrical surface 13 and the inside cylindrical surface 14, and the half members 1 of one pair are rotatable around the central axis thereof with respect to the half members 1 of another pair.
When one pair of the half members 1 is coupled to each other, the cylindrical portions 2 of the two members form a fully cylindrical portion 15 in the middle of the half members 1. The inside cylindrical surface 14 has an inside diameter that is slightly greater than the outside diameter of the cylindrical portion 15, and one pair of the previously installed half members 1 and another pair of the presently installed half members 1 can be slightly inclined with respect to each other when they are installed. The inside cylindrical surface 14 of the presently installed half members 1 cannot be detached from the outside cylindrical surface 13 of the previously installed half members 1 when the two pairs of the half members 1 are connected in series.
When one pair of the half members 1 of the conventional submarine cable protecting device 9 is coupled to each other, four pairs of the bolts 11 and the nuts 12 must be attached and the bolts 11 and the nuts 12 must be tightened together. Therefore, it takes a long time to carry out the installing work of the submarine cable 8 by using the conventional submarine cable protecting device 9.
The assembly of the half members 1 of the conventional submarine cable protecting device 9 must be manually performed by using the bolts 11 and the nuts 12, and it is difficult to efficiently install the submarine cable 8 when the conventional submarine cable protecting device 9 is used.
Further, in the case of the conventional submarine cable protecting device 9, it is necessary that the installation of the pairs of the half members 1 be performed in series in one direction only. For example, if the pairs of the half members 1 are continuously installed in series starting from two separate locations, it is quite difficult to make the length of the finally-installed pair of the half members 1 equal to a remaining distance between the end of the pairs of the half members 1 already installed from one location and the end of the pairs of the half members 1 already installed from the other locations. If the length of the finally-installed pair of the half members 1 is not equal to the remaining distance, the installation of the pairs of the half members 1 cannot be finished. Therefore, it is practically difficult to facilitate the installation of the pairs of the half members 1 in series when the conventional submarine cable protecting device 9 is used.